Multilayer oriented antimicrobial and antifogging films

ABSTRACT

Antimicrobial and antifogging polymeric films with preferable A/C/E structure useful for the food, medicine and agriculture applications as well as for other general packaging and non-traditional special applications. More preferably, antimicrobial and antifogging films having a A/B/C/E structure. Most preferably, antimicrobial and antifogging films having a A/B/C/D/E structure. A multilayer structure (having at least an skin layer (A) having antifogging and antimicrobial properties/ a core layer (C) / an outer layer (E) structure) for semi and biaxially oriented polyolefin based antifogging films having advantageous properties as compared with known and commercial films such as low values of haze, high values of sheen, lower longitudinal and transverse shrinkage, which provides high dimensional stability, and excellent antifogging and antimicrobial properties. Preferably the skin layer (A), having antifogging and antimicrobial properties, is electrical corona or flame treated. Electrical corona or flame treatment of the outer layer (E) may enhance ink anchorage and increase the printability of this layer. Preferably, the films comprise an inner (B) layer between the skin layer (A) and the core layer (C). Preferably, the films may comprise a second inner (D) layer between the outer (E) layer and the core layer (C).

FIELD OF THE INVENTION

The present invention relates to the field of plastic fabrication anduses. More specifically, the present invention relates to multilayeredplastic films that have antifogging and antimicrobial properties.

BACKGROUND

It is known that many thermoplastic polymer packaging materials, such asfilms, coatings, sheets, bags, and the like, with suitable strength andflexibility are used to enclose perishable foods, fruits, raw meats,daily dishes and vegetables. These packaging materials tend to discolorand fog during extended storage. Because of this, polymer packagingmaterials have to possess the following characteristics: (1) suitablethickness and cohesive properties for packaging, (2) high antifoggingproperties, i.e. the films do not accumulate water droplets on thesurface of the material, (3) high mechanical strength at break, (4)appropriate slip properties, (5) excellent optical characteristics, suchas gloss and transparency, and (6) sealability under heat.

There is a high demand in the packaging food industry, agriculture,industrial markets, flower wrapping trade, and the like for biaxiallyoriented thin antifogging films of different types that can be used forboth food-wrapping and agricultural applications. The antifogging andantimicrobial films reduce the growth of living contaminants (such asbacteria and molds) and ensure that any condensation of water vaporoccurs as an uniform, invisible, layer of water rather than as a seriesof individual droplets which are not only aesthetically undesirable butproduce damaging effects.

The several goals of these films are: (1) to ensure that the polymerthin films retain their transparency so that the packaged contents areclearly visible and so that there is maximum light transmission into theenclosure, (2) to protect the packaged food products from undesireddegradation that may be caused by the droplets of water, (3) to preventlarge drops of condensed water from falling onto young plants,increasing the possibility of damage and disease, (4) to prevent plant“burning” caused by large drops of water lensing (concentrating andfocusing) solar radiation onto the contents of the package, (5) toprovide antimicrobial properties and (6) to provide prolonged shelf lifeby preventing the growth of the certain bacteria.

Currently, antifogging films (also known as antifog or antimist films)are produced by adding or coating various types of organic antifoggingadditives, such as ethoxylated sorbitan ester, glyceride fatty acidester, glycerol stearate (or monostearate), glycerol oleate and sorbitanester, and the like, to conventional film forming polymers, such aspolyolefins, flexible vinyl chloride polymers, oriented styrenepolymers, polyesters, ethylene-vinyl acetate copolymers, and the like.

There are a number of available patent publications related toantifogging polymer films obtained by using different types ofthermoplastic film-forming/antifogging additives as discussed below.These patents relate to systems such as a biaxially stretched film witha base of an olefin polymer resin composition containingethylene-propylene copolymer and 0.5% of polyethylene glycol stearylether, olefin polymer/fatty acid monoester of polyhydric alcohol (oralkaline metal salt of a diester of sulfosuccinic acid),polyolefin/ethylene oxide (or monoglyceride of a fatty acid),polystyrene/alkyl phenyl polyethylene glycol ether (of fatty alcoholsulfate) base coating, polyethylene/polyhydric alcohol esters or metalsalts of either saturated or unsaturated monocarboxylic fatty acids,ethylene polymer and polybutene blend/glyceride with acyl group, andethylene-acrylic acid (or ethyl acrylate and/or vinyl acetate)copolymers or low density ethylene polymers/alkyl phenyl polyethyleneglycol ethers or alkoxylated alkyl phenol. But all of these patentssuffer from one or more of the following disadvantages such as higherhaze values, low values of sheen, higher transverse or longitudinalshrinkage, and poor antifogging properties.

More specifically, in U.S. Pat. No. 4,066,811, there is disclosed rawtubular polyolefin films with suitable orientation determined by heatshrinkage, containing ethylene-vinyl acetate copolymer, polyethylene,polypropylene or mixtures thereof, polyalkylene ether polyol andnon-ionic surfactant-polyhydric alcohol ester derivatives of fattyacids. In the above patent, the determination of antifogging propertiesof the subject film was according to the following measurements: (1) nowater droplets were present on the surface and water was in a uniformlayer, (2) large water droplets locally were adhered or there wasunevenness in the state of any adhering water droplets, and (3) finewater droplets adhered to the whole surface.

Other recently published patented inventions, such as JP Pat.09-104,092, relate to various polymer compositions, sheets, and filmshaving fog resistant properties. Disclosed therein are antifoggingsheets comprising weather-resistant polycarbonate based films, hot-meltpoly(methylmethacrylate) films containing a benzotriazol UV-absorber,and cellulose films containing a diethyl phthalate plasticizer, to forma flat or wavy laminated panel allegedly providing good weather andmoisture resistant adhesion.

Antifogging polypropylene lids with smooth handling properties, such asdisclosed in JP Pat. 09-76,339, were prepared by thermal formation ofpolypropylene sheets, where the interior faces of the lids exhibitantifogging property and the exterior faces have a friction coefficientof 0.01-0.7. The plastic of these lids was stretched in the machinedirection, coated on the exterior face with poly(dimethylsiloxane) andon the interior face with sugar fatty ester emulsion, and thermal formedinto a lid showing no noise when removed from their stack.

Plastic sheets having anisotropic surface characteristics, includingfogging and adhesion properties, are disclosed in JP Pat. 09-85,847 andcomprise alternating strips of nylon 6-12 and ethylene-methacrylic acidcopolymer.

There are antifogging laminated films for agricultural uses that use apolyolefin resin middle layer. This layer frequently consists of highdensity polyethylene and synthetic rubber with external layersconsisting of antifogging agents. One laminate, disclosed in JP Pat.0994,930, comprises an ethylene-vinyl acetate copolymer middle layer,uses KFG 561 as an antifogging agent, and showed good blockingresistance, mechanical strength and fogging presentation (45° C. waterfor 45 days or 0° C. environment and 20° C. water for 24 hours).

Other agricultural antifogging films, such as the ones disclosed in JPPat. 09-95,545, were prepared using olefin copolymer compositionscontaining sulfonated olefin copolymers, ethylene-C₃₋₁₂ olefins, andethylene-acrylic copolymers. The olefin copolymers were synthesized bypolymerization of olefins in the presence of metallocene (Zr) catalystcontaining silica and methylaluminoxane. More specifically, atransparent antifogging film was prepared from a mixture of 80%sulfonated olefin polymer (reaction product of butane sulfonate withethylene-acrylic copolymer) and 20% of ethylene-hexene-1 copolymer whichwas polymerized in the presence of a catalyst system containing silica,methylaluminoxane, bis(1,3-n-butylmethyl cyclopentadienyl)zirconiumdichloride and triisobutylaluminum.

JP Pat. 09-77,938 discloses a polymer composition with good slidingproperties that comprises 10-60% of graft copolymers manufactured bygrafting an elastomer with ≧1 layers of antifogging agent KFG 561. Theresultant laminate used ethylene-vinyl alcohol copolymer as a middlelayer, 20% of hydrogenated butadiene-styrene elastomer as an innerlayer, and 10% of the said elastomer outer layer comprises a fireretardant agent and showed good blocking resistance, mechanicalproperties, dust, and fogging presentation.

Fluoropolymer films with wetting ≧35 dyn cm, as disclosed in JP Pat.09-136,980, were mixed with antifogging agents comprising water-thinnedacrylic polymer emulsions, such as ethylacrylate-2-hydroxyethylmethacrylate-2-hydroxymethacryloxybenzophonone-methylmethacrylate copolymer, and colloidal SiO₂. Films prepared according tothis patent showed reasonably good antifogging property for 7 months.

Two Japanese patent inventions, JP Pat. 09-165,178 and JP Pat.09-165,447, disclose heat-aging and light-resistant propylene polymercompositions causing no fogging of glass for use in automotiveinteriors. These compositions contain (A) crystalline polypropylene, (B)inorganic filler, such as TiO₂, (C) ethylene-propylene elastomer, and(D) conventional stabilizers, antioxidants, antiblocking agents, andother additives such as epoxy resins, hydroxyl-containing low molecularweight polyolefins, polyethylene waxes, and anionic surfactants. Platesprepared from this composition by kneading, pelleting, and injectionmolding show 150° C. oven life for 320 hours. The plate and glass platewere left in a sealed container at 120° C. for 20 hours and showed ahaze of the glass of 0.8%.

In another patent entitled “Fog-Resistant Heat-sealable Film”, U.S. Pat.No. 4,341,825, there is disclosed a transparent, heat-sealable,laminated film that has a first layer of a difficulty heat-sealablepolymer, such as an axially oriented polyethylene terephthalate filmwith 0.002-0.006 cm thickness, and a second layer of a readilyheat-sealable polymer, such as low density polyethylene and copolymersof ethylene with acrylic acid, ethyl acrylate and vinyl acetate,chemically interfacially joined to the first film layer. The said secondfilm layer comprises 0.2-0.7% of an alkyl phenyl polyethylene glycolether of the formula, R—C₆H₄—O—(CH₂)_(n)OR′—OH, where R-alkyl C₁₀₋₁₅ andalkylene C₄₋₁₀ as an antifogging agent. The resulting laminated film isthen heated to 130° C. and exposed to UV-light through the second filmlayer for a time and at an intensity sufficient to cause the formulationof the chemically interfacial bond between the two layers. The filmobtained resists the formation of fog when utilized to packagerefrigerated foods. However, the disadvantages of this invention can benoted as the following: (1) the subject film comprises two layerscontaining non-oriented ethylene polymers, (2) the subject film has ahigh thickness, (3) the subject film has a high content of antifoggingagents as compared with more conventional polymer fog-resistant films,and (4) the antifogging agents used in the subject film were synthesizedby reaction of alkyl phenol with polyethylene oxides. In this case, thetrace of the phenol will be present in the product synthesized. This canlimit the use of this specific additive in the food packaging industry.

Another patent, entitled “Fog-Resistant Olefin Polymer Films”, U.S. Pat.No. 4,486,552, discloses a film-forming composition for making packagingfilms that are resistant to fogging, especially when employed as apackaging film for moist products. The subject film of this patentcomprises an ethylene polymer, especially a linear low densitypolyethylene, and 0.5-2.0% of antifogging agents, such as an ethoxylatedalkyl phenol along with a mixed mono-, di-, and/or triglyceride, apolyoxyalkylene fatty acid ester or various combinations of saidadditives. The mixing of the antifogging agents into the ethylenepolymers, which can be LDPE, LLDPE, HDPE, ethylene-octene-1, or blendsor alloys of said olefin polymers, is done by mixing the antifoggingagents into molten polymer by commonly used techniques, such asroll-milling, mixing in a Banbury type mixer, mixing in an extruderbarrel, or the like. The subject film was formulated as 0.015 mm on acast film unit at 260° C. melt temperature and chill roll temperature of18° C. It is noted that the films prepared according to this patent havea relatively high fog resistance when compared with commerciallyavailable plasticized poly(vinyl chloride) films, such as the onedisclosed in U.S. Pat. No. 4,072,790. Further, other high qualities areproduced, such as improved transparency (64.3 against 5.0 for PVC),gloss (95.9 against 89.0), haze (1.0% against 2.0%), lower heat sealrange (121-127° C. against 149-177° C.), and overall toughness, ascompared to PVC films. However, it was shown that the antifogging agentsused in this patent exude to the surface of the film withinapproximately 48 hours after fabrication. The subject films of thispatent have the following disadvantages: (1) the films are notmulti-layered and biaxially oriented, (2) the films have a highthickness and high density resulting in a low yield, (3) there is a lowheat-sealing temperature, (4) there are low values of surface andmechanical characteristics, the film surfaces are not treated by coronadischarge, and (5) the film comprises relatively high concentrations ofantifogging agents used in the polymer composition.

U.S. Pat. No. 4,876,146 and 4,956,209, disclose “Anti-foggingMulti-layered Film and Bag Produced Therefrom for Packaging Vegetablesand Fruits”. These patents describe biaxially oriented and multilayeredantifogging polyolefin films useful for packaging fresh vegetables andfruits comprising: (A) a 4-100 μm base layer formed from polypropyleneor ethylene-(5%)-propylene copolymer or ethylene-vinyl acetate (acrylicacid or styrene) copolymer; and (B) one or two surface layers that are0.3-8.0 μm thick and having heat-sealable properties resulting from a(1:1) mixture of propylene-butene-1 (18%) and ethylene (3.5%)-butene-1copolymers containing 0.3-3.0% antifogging agent such as higher fattyacid ester of monoglyceride (or alkyldialcoholoamide, polyalkyleneglycol, polyalkylene glycol alkylphenol ether). There are also otherconventional additives, such as antistatic and lubricating agents. Inaccordance with said patent it is possible to incorporate theantifogging agent only in a base layer of the film so that theantifogging agent migrates to and diffuses into the surface layer(s)after laminating the layers. This migration and incorporation of theantifogging agents into the surface layers provides the antifoggingproperty important to the surface layer. Antifogging properties wereobserved, the film was formed as a bag and “Shtitake” mushroom wereenclosed in the bag; the temperature was varied twice per day with arise and drop between 20 and 40° C.; the result was observed after 1day. There was little fogging, discoloration, and the measured surfacetensions were 38-42 dyne/cm. The disadvantages of the films prepared inaccordance with said patent included: (1) high values of haze (3.1%),(2) low values of sheen (86.6%), (3) coloring agent in the film does notcomply with food contact standards of the U.S. FDA, (4) theidentification of fogging properties used a non-effective method, (5)the films had low performances as antifogging surfaces, i.e.discontinuous film of water is observed on the surface, (6) E-P-Bterpolymer is not used in the surface layers, (7) ethylene-vinyl acetatecopolymers are used in the base layer and most probably for improvementof barrier properties of films, and (8) present patent is limited tousing 2-3 layered films. U.S. Pat. Nos. 4,876,146 and 4,956,209 whichare hereby incorporated by reference.

All of the patents previously mentioned above, however, suffer from nothaving antimicrobial properties.

In the recent years, essentially growing trend is the use of variousbioactive agents, including predominantly ecologically puremetal-containing biocides in polymer production industries forpreparation of antimicrobial, antibacterial and antifungal polymermaterials such as films, sheets, coatings, plastics, fibers, composits,etc. The number of patent publications in this field have increased inrecent years. The following references have attempted to addressantimicrobial films:

(1) U.S. Pat. No. 4,938,955, 1990 discloses an antibiotic resincomposition comprising at least one antibiotic zeolite of whichion-exchangable ions are partially or completely replaced with ammoniumions (5-15%) and antibiotic metal ions (Ag⁺ of 1-15%), at least onediscoloration inhibitor such as benzotriazole, oxalide, anilide,salicylic acid, phosphous, sulfur, etc. compounds and at least onepolymer resin (this composition exhibits antibiotic property and doesnot discolour with time, and can be employed to form a variety ofproducts which require antibacterial and/or antifungus properties);(2) Transparent bactericidal multilayer sheets with haze <5% comprise acrystalline thermoplastic resin containing 0.05-5 phr granular zeolitecontaining bactericidal metal ions in a sheet comprised polypropylenecontaining 0.5% Bacterikiller BM 103 (zeolite A containing 3.5% Ag) [JPPat. 04,275,142 (1992), Chisso Co., Japan]; (3) Antibacterial polyolefincompositions with inhibiting effects on the growth of bacteria andmoulds contain polyolefins and 2-pyridinethiol 1-oxide and its metal(Zn) salts or other organic biocides (polypropylene 100,2-(4-thioazolyl) benzimidazole 0.25 and Zn 2-pyridinethiol 1-oxide 0.25part were roll kneaded at 230° C. and then hot pressed at 220° C. togive a 2 mm sheet, which completely inhibited of the growth ofAspergillus niger, Penicillium citrinium, Chaetomium globosum,Aurebasidium dulllans, and Gliocladium virens at 28° C. for 28 days) [JPPat. 04,270,742 (1992), Shinto Paint Co. Ltd., Japan]; (4) Antibacterialheat-resistant polyolefin compositions comprising polyolefins(polypropylene)100, bactericidal metal ions (Ag, Cu, Zn and/or Sn ionssupported on zeolites) 0.01-1.5, dimethylsiloxane oil 0.01-0.2, andaluminium borate whisker (9Al₂O₃.2B₂O₃) 0.01-0.1 part showed goodantibacterial action as tested against colon bacilli [JP Pat. 04,363,346(1992), Tonen Kakagu Kk., Japan]; (5) JP 04,13,733 (1992) disclosesantibacterial films for packaging chemicals and food which were preparedby treating one or two surfaces of films containing aluminosilicic acidsalts with electrical corona (a composition containing 2 parts zeolite A(Ag content 6.7%, NH₄ content 0.5%) and polyamide (6-nylon 66 copolymer)were together extruded and exposed to electrical corona for 0.2-10 s togive an antibacterial film with good adhesion to ham, versus pooradhesion for the film not treated with said corona); (6) U.S. Pat. No.5,614,568, 1995 (Mawatari, M., et al., Japan Synthetic Rubber Co., Ltd.,Tokyo) claimed an antibacterial resin comprising (A) 100 parts by weightof aromatic alkenyl resin, specifically styrene resin, (B) 0.01-30 partsof an inorganic metal compound or a porous structure substrate which hasbeen injected to ion-exchange with a metal ion selected from the groupconsisting Ag, Zn, Hg, Sn, Pb, Cd, Cr, Co, Ni, Mg, Fe, Sb and Ba, and(C) 0.01-30 parts of a polyethylene comprising —COOH, —COOM(salts), —OH,—COOR, and epoxy, anhydride and amine functional groups, a polypropylenecomprising said selective functional groups with molecular weight10000-30000; (7) Japan Chem. Ind. Co. (JP Pat. 09,176,370, 1997)discloses an antimicrobial injection-moldable polypropylene compositionshowing no discoloration or degradation during processing, storage anduses contain 0.2 phr of liquid paraffin, 1.0 phr of the mixture ofinorganic compounds Ag_(0.15)Na_(0.5)H_(0.35), Zr₂(PO₄)₃ andMg_(0.7)Al_(0.3)O_(1.15) which was used as an antimicrobial agent; (8)Polyethylene terephthalate films coated with thin Ag, Cu and Ti-layersby sputtering treatments have high antibacterial activity. The reducingin bacteria values of almost 100% were determined by the SEK Shake FlaskMethod and the Contacted Film Method [S. Kubota, et al, Bakin Bobai, 25(7), 393 (1997); Chem. Abstr., 127, 122386s (1997)]; (9) Tokuda, et al,[JP Pat. 09,136,973, 1997] describes bactericidal packaging filmscomprising thermoplastic resins or blends on the base of PE, PP, PVC,polyesters and/or PS and calcined powder ceramics containing 40-60% ofSiO₂, 20-30% of Al₂O₃, 4-8% of ZnO, 2-5% TiO₂ and 0.1-1.0% Ag or Cusalts as an antibacterial agent (these films were prepared by mixingabove ceramics with said polymers and forming into films or by spreadingor printing above ceramic-containing resins on resin base films); (10)JP Pat. 09,123,264 (1997) discloses antibacterial decorative sheets andmanufacture of decorative moldings (these sheets were prepared byshaking colored base sheets with thermosetting diallyl phthalate resincomposition containing 0.5% of Ag/Zr phthalate, Ag tripolyphosphate, Aghydroxyapatite, and/or (Ag/Ca)₃ phosphate. A printed paper sheet was hotpressed with a moldable polymer composition to form a waterproof pan forbathroom uses); (11) Bactericide-containing abrasive agents and resinmoldings for video and arcade games comprise a thermoplastic resin (98%of polycarbonate) incorporated with fillers (1%) and bactericides(Ag-containing zeolite, Bactekiller) or bactericide-treated powders (1%)[Sumitomo Elect. Ind. Ltd., JP Pat. 09,77,880, 1997]; (12) JP Pat.09,77,042 (1997) releases to antimicrobial synthetic resin containersfor preserving drinking water (this container is prepared usingsynthetic resins with Ag-containing glass particles that releaseadequate amount of microbiocidal silver ions (Ag⁺) into the water wheregrowth of bacteria or fungi in the drinking water is prevented by theseions); (13) JP Pat. 09,002,517, 1998 [Taisho Pharmaceutical Co. Ltd.(Tokyo, Japan)] discloses a process for making a bottle and cap withantibacterial properties on their inner contact surfaces. Antimicrobialzeolite power (1 to 5% by weight) containing microbiocidal Ag, Zn and Cuions is mixed with thermoplastic resins such as ethylene-vinylacetatecopolymer, polypropylene and polyethylene (the zeolite is dispersedthroughout the bottle and is present on both inner and outer surfacesand can also be used for both cap and membrane seal); (14) Polypropyleneplastic table wares contain an antimicrobial agent (Amenitor) (JP Pat.09,108,084, 1997); (15) Bactericide power (Bactekiller) orbactericide-treated power containing adhesive agent and resin moldingsfor video areade games were described (Chem. Abstr., 127, 35460t, 1997);(16) Silver (Ag)-zeolite antimicrobial agents for protection of theplastic films from various microorganisms were manufactered by MichubusiCo. Bactericide ceramic power containing 0.1-1.0% Ag or Cu, 2-5% TiO₂,4-8% ZnO or MnO₂, 20-30% Al₂O₃ and 40-60% SiC or SiO₂ was recommended touse in the varoious thermoplastic composition (polyolefin, polystyrene,polyesters, etc.), resins and binders [T. Ishitaki, High Polym. Japan,39(10), 744 (1990); Y. Kajiura, Jidosha Gijutsu, 51(5), 34 (1997); JPPat. 09,136, 973 (1997)]; (17) Antimicrobial activities of some newcoordination polymers were also discribed by Patel, et al. [B. Patel andM. Mohon, J. Polym. Mater., 13(4), 261 (1996)].

However, all these publications are related to the preparation and useof various antimicrobial polymer materials including non-orientated andnon-multilayered polymer films, sheet, etc. containing bioactive metalions. Thus the above patents describe inventions are essentiallydifferent from the present patent invention which is concerned withpreparation of semi- and biaxialy oriented and multilayeredantimicrobial thin films containing Ag⁺-containing polymeric bioactiveagent only in the skin layer and having high physico-mechanical, thermaland antimicrobial properties. Another distinctive feature of these filmsis possibility of their use in the food packaging applications, whereanti-fogging properties are required.

Several Firms such as Taisho Pharmaceutical Co. Ltd. (Tokyo, Japan),Kanebo Chemical Industries, Ltd. (Osaka, Japan), M. A. Hanna Company(USA, Neutrabac™ Antibacterial Masterbatch), Wells Plastic Ltd.(Staffordshire, UK), etc. have already started to manufacture organicand inorganic antibacterial agents and various antimicrobialMasterbatches for use in thermoplastic polymer compositions.

Many organic and organoelement compounds having high biologicalactivities are also used in polymer film-forming composition systems [Z.M. Rzaev, CHEMTECH, (1),58 (1976); Z. M. Rzaev et al., England Pat.1,270,922 (1972); U.S. Pat. No. 4,261,914 (1981); U.S. Pat. No.4,314,851 (1982); Z. M. Rzaev et al., Bioresistant Organotin Polymers,Chemistry, Moscow, 1996 (Russ.)]. Thus, (1) “ICI Biocides” Firm (UK)prepared and patented new water soluble biocides on the base ofisothioazolione useful for the effective preservation of polymer resins,specially aqueous-based paints from bio-destruction with microorganismsin the stage of synthesis, storage and uses of these materials [C. L. P.Eacoff, Orient. J. Oil and Colour Chem. Assoc., 74 (9), 322 (1991)]; (2)Polen Kagaku Sangyo K.K. [JP Pat. 09,169,073, 1997] disclosesantibacterial and antifungal sheets laminated with low expanded olefinpolymer (such as HDPE) compositions containing 0.1-1.0%2-(4-thioazolyl)benzimidazole as an antibacterial and antifungal agentshowing good deep drawability; (3) Antimicrobial rubber articles containammonium salt of chlorohexidine as an antimicrobial agent [UK Pat.8,919,152 (1990)]; (4) Biocide Cl-containing polyketones havingantibacterial activity against selected yeast, fungi,—and bacteria wereprepared by Fiedel-Graft [Friedel-Craft] reaction of o-cresol withchloroacetyl chloride, dichloromethane and dichloroethane in thepresence of anhydrous AlCl₃ as a catalyst in nitrobenzene as solvent [B.T. Petel, et al, Orient. J. Chem., 13 (1), 83 (1997); Chem. Abstr., 127,136122q (1997)]; (5) Polyethylene four-layered film was coated withmixture of allyl isothiocyanate (as a biocide), polyfunctionalisocyanate, polyols and dibutyltin laurate (as a catalyst) to give amultilayered film with polyethylene outer layer having antibacterialactivity [JP Pat. 09,151,317, 1997]; (6) Matsukawa Electric Works, Ltd.(Japan) was disclosed a method of preparing plastic table wares (plasticbowl) containing antimicrobial agents (Amenitop) by moulding. The corepotion is formed with a polypropylene resin and this is coated withanother polypropylene containing a said antimicrobial agent; (7) KyowaCo. Ltd. [JP Pat. 09,135,716, 1997] patented the gas-permeable andantimicrobial bags for the medical application. These bags were preparedfrom cushion bases consisting open-celled polymer foams andbactericide-containing hydrophobic noncircular fiber; (8) p-Hydroxybutylbenzoate [JP Pat. 63,173,723 (1988)],2-(4′-thiazolyl)-benzimidazole [U.S. Pat. No. 4,008,351 (1977)],Pt-vinylsiloxane complex [JP Pat. 04,202,313 (1993)], polymeric iodinecomplexes [U.S. Pat. No. 3,907,720 (1975), phosphate esters [U.S. Pat.No. 3,888,978 (1975), U.S. Pat. No. 3,991,187 (1976), U.S. Pat. No.4,661,477 (1987), U.S. Pat. No. 4,935,232 (1990)] and2,3,5,6-tetrachloromethylsulfonylpyridine (for preparation antibacterialstyrene type resin compositions) [JP Pat. 07,82,440 (1995)] have alsobeen recommended for use as bactericide and antimicrobial agent in thevarious polymer compositions, film and sheets.

There are a number of patents disclosing various polymer composits,thermoplastic fibers, sheets, coatings, films, etc. having biologicalactivity toward different type of microorganisms [Shima et al., U.S.Pat. No. 4,000,102, 1976; Dell et al., U.S. Pat. No. 4,584,192, 1986;Fink et al., U.S. Pat. No. 4,751,141, 1988; Gillete et al., U.S. Pat.No. 5,152,946, 1992; Grighton et al., U.S. Pat. No. 5,246,659, 1993;5,104,306, Apr. 14, 1992]. For example, (1) U.S. Pat. No. 5,178,495,1993 discloses a polymeric film with biocide. A multi-ply film has beendeveloped that includes a biocide in at least one the film layers. Saidbiocide mixed with the thermoplastic prior to extrusion of the sheet.This sheet with biocide can be used to construct water containmentfacilities for drinking water, fish farms and industrial use and can beused as a covering for water tanks or equipment in environments thatpromote microbial growth at the surface of the film; (2) U.S. Pat. No.5,777,010 1998 (Nohr R. S., et al., Kimberly-Clark Worlwide, Inc.,Neenah, Wis.) discloses melt-extrudable composition containingantimicrobial siloxane quaternary ammonium salts. These compositionswhich includes a thermoplastic polyolefin and a siloxane quaternaryammonium salt additive. Upon melt extruding the thermoplasticcomposition to form fibers and non-woven webs, or other shaped artides,the surfaces of such shaped articles exhibit antimicrobial properties.(3) Early, antimicrobial siloxane quaternary ammonium salts werepatented [U.S. Pat. No. 5,567,372, 1994 and U.S. Pat. No. 5.569,732,1994] and published [ Nohr R. S., et al., J. Biomed. Sci., Polym. Ed.,5(6), 607 (1994)] (U.S. Pat. No. 5,567,372, 1994 discloses a method ofpreparing a non-woven web containing antimicrobial siloxane quaternaryammonium salts); (4) U.S. Pat. No. 5,527,570 [Addeo, A., et al.,1996,Centro Sviluppo Settori Impiego SRL, Milan, Italy)] relates to amultilayer and multifunctional packaging elements having high-absorptionactivity toward aqueous liquid substances as well as barrier propertiestoward gases such as oxygen and carbon dioxide are prepared bythermoforming (Each layer comprises a polymeric thermoplastic material.Intermediate layer of this packaging element may also containantibacterial agents); (5) U.S. Pat. No. 5,142,010, 1992 (Olstein, A. D.et al., H. B. Fuller Licensing & Financing Inc., Wilmington, Del.)discloses polymeric biocidal agents containing carboxyl groups, fluorenesubstitute and alkyl C₁₋₂₀ groups, and any bioactive naturally occurringamino-acid chain (the resulting polymers are disclosed to be useful inany variety of applications requiring an antimicrobial agent or anactive sanitizer or disinfectant including films, coatings andadhesives, as well as also being useful in medial, food preparation andpersonal care product applications; (6) Describes an antimicrobialfilm-forming compositions containing bioactive polymers (homo-, co- andterpolymers of monomers containing pyran groups) having pendant pyrangroups [Greenwald R. B. et al., U.S. Pat. No. 5,108,740, 1992, EcolabInc., St. Paul, Minn.] (this publication describes a liquid compositionthat yields an abrasion resistant polymeric film on a surface thatprovides extended protection from microbial growth through slow releaseof a potent antimicrobial agent).

As evident from the above described patent publications, there isrelatively small number of patent publications describing polyolefinbased, in particular, mono- and biaxially oriented polyolefin basedfilms, and all of patent publications suffer from one or more of thefollowing properties: not being multilayered and oriented polyolefinnon-opaque films, not being heat-sealable; not having antimicrobialproperties using thin films containing Ag⁺-containing polymericbioactive agent only in the skin layer, not having antifoggingproperties.

SUMMARY

It is an object of the present invention to design and prepare amultilayer structure (having at least an antifogging and antimicrobialskin layer (A)/a core layer (C)/an outer layer (E) structure) for semiand biaxially oriented polyolefin based antifogging films havingadvantageous properties as compared with known and commercial films suchas low values of haze, high values of sheen, lower longitudinal andtransverse shrinkage, which provides high dimensional stability, andexcellent antifogging and antimicrobial properties. Preferably theantifogging and antimicrobial skin layer (A) is electrical corona orflame treated. Electrical corona or flame treatment of the the outerlayer (E) may enhance ink anchorage and increase the printability ofthis layer. Preferably, the films comprise an inner (B) layer betweenthe antifogging and antimicrobial skin layer (A) and the core layer (C).More preferably, the inner (B) layer has the same composition asantifogging and antimicrobial skin layer (A) without the antimicrobialadditives. Preferably, the films may comprise a second inner (D) layerbetween the outer (E) layer and the core layer (C). More preferably, thesecond inner (D) layer has a preferred composition of 100 percent (%)E-P-B terpolymer.

Antimicrobial and antifogging ≧3 layers polymer films with preferableA/C/E structure useful for the food, medicine and agricultureapplications as well as for other general packaging and non-traditionalspecial applications. More preferably, antimicrobial and antifoggingfilms having a A/B/C/E structure. Most preferably, biaxially orientedpolypropylene films having symetrical structure A/B/C/D/E, where twoouter layers A and E are having antimicrobial and antifogging propertiesand heatsealable and two intermediate layers B and D are made of E-Prandom copolymers or E-P-B terpolymers, with or without antifoggingagents.

A preferred embodiment of antifogging and antimicrobial skin layer (A)comprises the following compositions: polypropylene greater than orequal to 1 percent (wt. %), E-P-B terpolymer or E-P random copolymergreater than or equal to 70 percent (wt. %), a mixture of glycerolmonostearate (GMS) and diethanolamine (DEA) greater than or equal to 0.2percent, special additive greater than or equal to 0.1 percent, anantiblocking agent greater than or equal to 0.2 percent (wt. %) ofsynthetic silica or zeolite and an antimicrobial agent greater than orequal to 0.1 percent (wt. %) of Ag⁺-containing inorganic polymer oflinear structure. More preferably, each component of skin layer (A) hasa percentage in the following ranges (the total of all components forany specific embodiment would, however, equal 100 percent (wt. %)):polypropylene between 1 and 5 percent (wt. %), E-P-B between 90 and 98percent (wt. %), a mixture of GMS and DEA between 0.2 and 0.5 percent(wt. %) where the GMS concentration in the mixture may vary from 1% to99%, and special additive (a mixture of higher fatty acid ester ofpolyvinyl alcohol or polyether polyol, where respective ratios may varyfrom 1% to 99%) between 0.1 and 0.5 percent (wt. %) and an antiblockingagent between 0.1 and 0.25 percent (wt. %) of synthetic silica,polymethylmetacrylite or zeolite and an antimicrobial agent between 0.2and 1.0 percent (wt. %) of Ag⁺-containing inorganic polymer of linearstructure.

Preferably, inner layer (B) has the composition totals: polypropylenegreater than or equal to 1 percent (wt. %), E-P-B terpolymer or E-Prandom copolymer greater than or equal to 70 percent (wt. %), and amixture of glycerol monostearate(GMS) and diethanolamine(DEA) greaterthan or equal to 0.2 percent, special additive greater than or equal to0.1 percent, More preferably, each component of antifogginner layer (B)has a percentage in the following ranges (the total of all componentsfor any specific embodiment would, however, equal 100 percent (%)):polypropylene between 1 and 5 percent (%), E-P-B between 90 and 98percent (%), a mixture of glycerol monostearate(GMS) anddiethanolamine(DEA) greater than or equal to 0.2 percent, specialadditive greater than or equal to 0.1 percent, an antiblocking agentgreater than or equal to 0.2 percent (wt. %) of synthetic silica. Morepreferably, each component of antifogging inner layer (B) has apercentage in the following ranges (the total of all components for anyspecific embodiment would, however, equal 100 percent (%)):polypropylene between 1 and 5 percent (%), E-P-B between 90 and 98percent (%), a mixture of GMS and DEA between 0.2 and 0.5 percent (wt.%) where the GMS concentration in the mixture may vary from 1% to 99%,and special additive (a mixture of higher fatty acid ester of polyvinylalcohol or polyether polyol, where respective ratios may vary from 1% to99%) between 0.1 and 0.5 percent (%) and an antiblocking agent between0.1 and 0.25 percent (wt. %) of synthetic silica or zeolite. This innerlayer does not have antimicrobial agent.

In a preferred embodiment, second inner Layer D has a preferredcomposition of 100 percent (%) E-P-B terpolymer or E-P random copolymerFurther, outer layer E has the same preferred and more preferredcompositions as either of layers A or D.

Finally, a preferred embodiment of core layer C comprises the followingcompositions (the total of all components for any specific embodimentwould, however, equal 100 percent (%)): polypropylene greater than orequal to 95 percent (wt %), a mixture of GMS and DEA , would be greaterthan or equal to 0.2 percent (wt %) and special additive equal orgreater than 0.1 percent (wt %) More preferably, each component of layerC has a percentage in the following ranges: polypropylene between 97.5and 99.5 percent (wt. %), a mixture of GMS and DEA between 0.2 and 0.5percent (wt. %) where the GMS concentration in the mixture may vary from1% to 99%, and special additive (a mixture of higher fatty acid ester ofpolyvinyl alcohol or polyether polyol, where respective ratios may varyfrom 1% to 99%) between 0.1 and 0.5 percent (wt. %)

Antifogging and Ag⁺-containing antimicrobial biaxially orientedpolypropylene (BOPP) films, can be prepared by using the tandem extrudersystem with two extruders supplied with two, three or four satelliteco-extruders, flat die, chill roll, corona discharge (onto the skinlayer or, alternatively, both the skin layer and the outer layer) andrecycling line as well as the mono- and semi-oriented cast filmtechnology with temperature controlled mold. After mono- and biaxiallystretching (4-7 times at 105-140° C. in the machine direction, MD and7-11 times at 150-190° C. in the transverse direction, TD) and aircorona discharged of one outer surface in the given conditions.Preferably, the antifogging and antimicrobial films have the followingcharacteristics: specific density of 0.91 g/cm³, low haze around 1.5%(+−0.2), high gloss greater than or equal to 95%, heat sealabilityaround 120° C., excellent dyne level retention (preferably equal orgreater than 40 dynes/cm) for good printability and antifoggingcharacteristics, excellent antifogging properties (rated ‘E’ accordingto ICI's cold fog test method, which means that the antifogging surfaceof the film is almost free of big water droplets which makes itinvisible) and excellent antimicrobial activity (99.9%) toward variousmicroorganisms, especially and preferably against three common bacteriaStaphylococcus aureus, Escherichia. coli and Salmonella enteritidis.

One the other hand, this invention also provides longer shelf life forthe freshcut and pre-packed vegetables, salads, fruits and like, due tothe high biological activity of the antimicrobial agent which preventsthe certain bacteria's growth. Another advantage of the presentinvention is the easy processability of the antimicrobial agent whoseprocessing conditions are within the processing windows of theingredients put in the conventionalal or antifogging BOPP films. In factthis advantage is provided by the high thermal stability of theantimicrobial agent which is >300° C. and which is well above of theoperating temperatures of the raw materials present in BOPP orantifogging BOPP films. In other words, under normal processingconditions of BOPP film manufacturing, the said antimicrobial agent doesnot show chemical degradation or decomposition.

Another important advantage of the present invention is the high degreeof antimicrobial performance against the certain bacteria by using onlya very low concentration of antimicrobial agent, due to its usage onlyin the very thin layer(s). This very low concentration of antimicrobialagent in the polymer matrix is preferably 30 times lower, as comparedwith conventional biocides used in known polymer compositions, due toits only use of a thin antifogging and antimicrobial skin layer (A),preferably between 0.5-1.5 μm. The usage of so low concentration ofantimicrobial agents advantageously reduces the cost of the film.

Another aspect of the present invention is the possibility to productionof the films in the form of mono-oriented and biaxialy orientedmultilayer thin films with similar component and layer compositions byusing cast film technology and tandem extruder system technology,respectively. According to the present invention the technologicalaspects of manufactured process of said films are (1) multilayered andmono-oriented cast film technology and (2) tandem extruder systemtechnology by the fact that tandem extruder system with two mainextruders for better homogenity and dispersion of the raw materials,supplied with three satellite co-extruders, recycling line and coronadischarge. The process is carried out by three chill-roll or water bathtreatments and two step of longitudinal orientation allowing to preparegood homogenized film with matte appearance having improved surfaceproperties and dimensional stability. The skin layer or, alternativelyboth the skin layer and the outer layer, of biaxially oriented filmsprepared may be treated in a known manner by flame or more preferably,by electrical corona discharge. The use of said recycling line for filmwaste forming in the transverse stretching stage allows to lower filmcost For example (as a preferred, but not the only embodiment of theprocess), after coextrusion, an extruded five-layer film is taken offover the corresponding process steps through a chill roll and cooled,and cast film profile is controlled by β-Gauge equipment. The film issubsequently stretched longitudinally at two steps and stretchedtransversely. After biaxially orientation, the film is set andelectrical corona-treated on one or two sides. The following conditionsare preferrable: (1) Extrusion: extrusion temperature 170-260° C., firstchill roll temperature 10-45° C.; (2) Machine (longitudinal) stretching:stretching roll temperature of first step 105-120° C. and second step115-140° C., longitudinal stretching ratio 4:1-6:1 for first step and1:1-1:2 for second step; Transverse stretching: temperature of heat-upzones 150-185° C., temperature of stretching zones 155-185° C.,transverse stretching ratio 7.5:1-11:1; Recycling: edges of thebiaxially orientated film is recycled and fed to the line again;Setting: setting temperature 165-185° C.; electrical corona discharge (Aside only or alternatively both A and E sides, together): voltage 10-25kV and frequency 1.5-30 kHz. The following preferable conditions for themultilayered mono-oriented (in MD only) antimicrobial films inaccordance with cast film technology in detail are selected: (1)extrusion temperature 250° C. by using temperature cotrolled MITSUBISHItype die, (2) chill roll temperature 10° C. (3)film profile iscontrolled by β-Gauge equipment, (3) the speed of film production line100 m/min, and (4) level of air corona discharge on A surface of thefilm is 11 Kw

It is further object of the present invention to widen the field ofapplication of said films useful for the food, medicine and agricultureapplications as well as for other general packaging and non-traditionalspecial applications including bioprotection of food contactingmaterials and food handling areas, medicine devices, agricultureproducts as well as applications in potential areas like food-storagecontainers, in oral hygienic products, hospitals and other healthinstitutions to provide hygienic conditions, for preserving drinkingwater and as a covering for water tanks, etc.

Another aspect of the present invention is to use new systems ofadditives, i.e—a mixture of GMS and DEA, special additive (a mixture ofhigher fatty acid ester of polyvinyl alcohol or polyether polyol) asantifogging agents, in combination with the antimicrobial agent Ag⁺, tocreate dual-effect polymeric films having both antifogging andantimicrobial properties.

Those additive systems are used with the following compatiblepolyolefins selected from polypropylene, a propylene-ethylene randomcopolymer, propylene-butene-1 random copolymer or anethylene-propylene-butene-1 terpolymer with various compositions, wherethe last three are used for the heat sealable skin layers.

Advantages of antifogging and antimicrobial films are: (1) Antimicrobialactivity against certain bacteria, (2) excellent antifogging properties(3) high antimicrobial performance in comparative low concentration ofantimicrobial agent, (4) preservation of antimicrobial activity duringthe long time of storage. of the polymeric films, even after corona orUV-treatment, (5) low total migration properties with the diluentsdistillated water, acetic acid, ethyl alcohol, heptane and olive oil asmentioned in the directives of EEC and FDA allowing to use of thesefilms in food packagings, (6) high optical properties (low haze, highsheen), (7)high physical-mechanical properties (8) possibility of usevarious thermoplastic film-forming polymers in core layer of films, and(9) wide range of conventional and special application fields ofinvented films.

DESCRIPTION

The present invention is an antifogging and antimicrobial film that is amulti-layered, oriented and made from polyolefins (polypropylene (PP),propylene-ethylene random copolymers, ethylene-butylene randomcopolymers and/or ethylene-propylene-butylene (E-P-B) terpolymers withvarious contents of E- and B- units). The present invention is usefulfor food packaging, food-wrapping, agricultural and horticulturalapplications, or any application where there is any condensation ofwater vapor on the various surfaces in the form of droplets andeffectiveness of certain bacteria needs to be reduced.

The following Examples of the present invention for preparation ofmultilayered antifogging and antimicrobial films with differentcomposition, properties are illustrated.

EXAMPLE 1

A first example of a multilayer film (A/C/E) having antifogging andantimicrobial properties comprises: (A) 1.0 μm antifogging andantimicrobial skin layer containing 92.25% by weight of saidethylene-propylene-n-butylene-1 terpolymer with given composition(ethylene [C₂]=1.5-4.5%, n-butylene-1 [C₄]=3.0-15.0%), 0.25% by weightof zeolite as an antiblocking agent, 6.0% by weight of polypropylenehomopolymer, and 1.0% by weight of Ag⁺—as an antibacterial andantimicrobial agent (in derived from a masterbatch having 20% activeagent-Ag.+, in a polypropylene carrier: the active is a “silvercontaining glass powder”, this has the CAS No: 65997-17-3, EINECS No:266-046-0, and EPA, Reg No: 73148 Issue date: 1 Sep. 2000), 0.20% byweight of glycerol monostearate and 0.20% by weight of diethanolamineand 0.10% by weight of special additive (a mixture of higher fatty acidester of polyvinylalcohol or polyether polyol) as antifogging andantistatic agent, (C) 28.0 μm core layer (C) from 99.5% by weight ofvirgin or marked (5-cholesten-3β-ol as a marking agent) polypropylenehomopolymer, 0.20% by weight of glycerol monostearate and 0.20% byweight of diethanolamine and 0.10% by weight of special additive (amixture of higher fatty acid ester of polyvinylalcohol or polyetherpolyol) as antifogging and antistatic agent and (E) 1.0 μm outer layerhaving 99.75% by weight E-P-B terpolymer and 0.25% by weight zeolite.This (E) layer does not exhibit any antifogging or antibacterialproperty. After biaxially stretching the film (5.5 times at 120° C. inthe (longitudinal direction, MD and 8 times at 170° C. in the transversedirection, TD) and electrical corona discharged skin layer (A). Layer(A) has corona treatment in order to accelerate the migration of theantifogging agents and alternatively, outer layer (E) has also coronatreatment for further printing purposes.

EXAMPLE 2

A second example of a multilayer film comprises the same thicknessstructure and composition as in Example 1 with the following changes:the core layer (C) comprises 100% of polypropylene homopolymer.

EXAMPLE 3

A third example of a multilayer film comprises an A/C/E structure butwith the following changes in Example 1: the antifogging andantimicrobial skin layer (A) is 1.5. μm thick, the core layer (C) is27.0 μm thick and the non-antifogging, non-antimicrobial outer layer (E)is 1.5. μm thick. After biaxially stretching, heat setting and coronadischarged in the given conditions, that film has antifogging andantibacterial properties on skin layer (A), whereas the outer layer (E)is useful for printing and heat seal applications.

EXAMPLE 4

A fourth example of a multilayer film comprises A/C/E thicknessstructure and composition as in Example 3 with following changes: Outerlayer (E) has also antifogging properties but no antimicrobial property.Thus, outer layer (E) has the same antifogging agents in layer (A) ofExample 1 but not Ag⁺ which provides antimicrobial effect. Film withthat structure is produced as described above.

EXAMPLE 5

A fifth example of a multilayer film comprises A/C/E thickness structureand composition as in Example 4 with following changes: Outer layer (E)has the antifogging and also antimicrobial properties where each oflayers (A) and (E) are 1.5 μm thick and have the chemical composition ofthe skin layer (A) in Example 1. The core layer (C) is 27.0 μm thick andhas the same chemical composition as given in Example 3. This film showsantifogging and antibacterial properties and corona treatment on bothsides.

EXAMPLE 6

A sixth example of a multilayer film comprises A/B/C/D/E structure withthe following changes in the Example 5: inner layer (B) and second innerlayer (D) has the same chemical compositions as skin layer (A) and outerlayer (E) where each of the four skin layers is of 0.75 μm thick. Thissymmetrical five layered composition provides the same excellentantifogging and antibacterial properties on both sides. Furthermore, thestructure of this example also avoids the low output capacity of thesingle satellite extruders which limits the total output of themanufacturing line by giving high total extrusion output. Coronadischarge on each side of this film also gives the flexibility of usingeither side by converters or packers.

EXAMPLE 7

A seventh example of a multilayered film comprises A/B/C/D structurewith following changes in Example 6: the second inner layer (D) becomesthe outer layer (E), having the same chemical composition of the layers(A) and (B) but with a thickness of 1.5 μm. This film exhibitsantifogging and antibacterial properties on both sides.

EXAMPLE 8

A eighth example of a multilayer film comprises A/B/C/D/E structure andchemical composition given in Example 6, except the thickness of thecore layer (C) which is 32.0 μm, giving the whole structure 35.0 μmtotal thickness.

EXAMPLE 9

A ninth example of a multilayer film comprises A/B/C/D/E structure andchemical composition given in Example 6, except the following changes:inner layer (B) and second inner layer (D) do not have the antimicrobialagent Ag⁺, and the thickness of the core layer (C) which is 22.0 μm,giving the whole structure 25.0 μm total thickness.

Layer compositions of the above mentioned examples were given in Table:1 and the physical-mechanical properties of those films were given inTable:2.

Analysis of the initial materials used and films prepared was doneaccording to known standard measurement methods. For example:

-   -   Specific density was determined according to ISO 1183 and/or        ASTM D-1505. Melt Flow Index (MFI) was measured according to an        ASTM 1238/L at 230° C. and under the load of 21.6 N. Melting        point (m.p.) was measured by DSC method, maximum point of the        melting curve, at a heating rate of 10° C./min. Vicat softening        point was determined according to ASTM D-1525. Izod impact        strength was measured according to ISO 180/1A. Tensile strength        and elongation at,break were determined according to ASTM D-882.        Haze of the film was measured according with ASTM D-1003.        Dynamic friction coefficient of the film was determined        according to ASTM D-1984. Sheen of the film was measured        according to ASTM D-2103, the angle of incidence was set at 45°.        Shrinkage of the film was measured according to ASTM D-2104. The        test sample was shrunk at 120° C. for a period of 5 minutes.        Water vapor transmission of the film was measured according with        ASTM E96. Oxygen permeability of the film was measured according        with ASTM D-1434. Surface tension of the film, after surface        ionization by electrical corona discharge and after storage for        6 months, was measured according to ASTM D-2578. Antifogging        property of the film was evaluated using ICI's the “Cold-Fog”        test method (ICI publication 90-6E) for food packaging film.

The “Cold-Fog” test results of the films according to the presentinvention (E1-E9), and known patented and commercial antifogging filmsare summarized in Table 3. The test method is as follows: put tap water,200 ml, in a 250 ml beaker and cover the top of the beaker with a sampleof the test film; place the beaker in a temperature controlledrefrigerator at 4° C. Observe the appearance of the film for a totalperiod of one week. It was shown that the films of the presentinvention, as compared with known patents and commercial films havesuperior antifogging appearance and properties.

The test method used to measure the antibacterial properties of thepresent invention is a viable count method. An inoculum, which is anutrient broth containing a known number of bacteria (there should be10⁵-10⁶ bacteria in the initial inoculum), is placed directly onto theBOPP film. A piece of standard (not antimicrobial) film is placed overthe inoculum to ensure intimate contact between the inoculum and thetest film and to prevent the inoculum drying out. The sample is coveredwith the lid of a petri dish and incubated at 35 deg C and 90% RelativeHumidity (ideal conditions for bacterial growth). After incubation theinoculum is washed off the samples, serially diluted and plated out ontoAgar plates. These plates are incubated and counts of the still viable(i.e. bacteria able to reproduce and form visible colonies) are counted.Antibacterial test results of the inoculum, commercial film and the filmof the present invention are as follows for each tested bacteriatype: 1) Salmonella enteritidis—Inoculum (initial—10⁶ bacteria; after 24hrs.—between 10⁷ and ¹⁰ ⁸ bacteria), Commercial Film without Antifoggingand Antibacterial Properties (initial—10⁶ bacteria; after 24hrs.—between 10⁷ and 10⁸ bacteria), and Film of Present Invention(initial—10⁶ bacteria; after 24 hrs.—between 10² and 10³ bacteria); 2)Staphococcus aureus —Inoculum (initial—¹⁰ ⁶ bacteria; after 24hrs.—approximately ¹⁰ ⁸ bacteria), Commercial Film without Antifoggingand Antibacterial Properties (initial—¹⁰ ⁶ bacteria; after 24hrs.—between 10⁸ and 10⁹ bacteria), and Film of Present Invention(initial—10⁶ bacteria; after 24 hrs.—approximately 10² bacteria); and 3)Escherichia coli—Inoculum (initial—10⁶ bacteria; after 24 hrs.—between10⁵ and 10⁶bacteria), Commercial Film without Antifogging andAntibacterial Properties (initial—¹⁰ ⁶ bacteria; after 24 hrs.—between10⁵ and 10⁶ bacteria), and Film of Present Invention (initial—10⁶bacteria; after 24 hrs.—approximately 10² bacteria).

Food contact approval tests of the present invention also had been done.Accordingly, Global Migration tests of the preferred embodiment filmexamples described herein have been found in compliance with thefollowing regulations: EEC Regulation 90/128/EEC and amendments (up toand including 99/91/EEC) and FDA Section 21 CFR Ch. 1 175.300 and176.170. The results for each Food Simulant (Test Conditions, MeanResult) are listed as follows: Olive oil (10 days @ 40° C., 2.0 mg/dm²),Distilled water (10 days @ 40° C., 0.2 mg/dm2). 3% w/w Ace. Acid (10days @ 40° C. 0.1 mg/dm²), 10% v/v EtoH (10 days @ 40° C., 0.2 mg/dm²),n-Heptan (30 mins @ 70° F., 0.9 mg/in²), Distilled water (24 hrs @ 120°F., <0.01 mg/in²), and 10% v/v EtoH (24 hrs @ 120° F., <0.01 mg/in²).

According to the present invention, the technological aspect ofmanufactured process of said films is distinguished from knownprocessing by using the tandem extruder system with two main extruderssupplied with two or three satellite co-extruders, recycling line andcorona discharge. Other processes of manufacturing said films are knownto those skilled in the art. The process is carried out by threechill-roll treatments and two steps of longitudinal orientation followedby the orientation in the transverse direction allowing the preparationof good homogenized antifogging films with improved surface propertiesand dimensional stability. One or both surface of biaxially orientedfilms prepared are treated in a known manner by corona discharge. Afterextrusion, the extruded film having at least 3 layers is taken off overthe corresponding process steps through a chill roll and cooled, andcast film profile is controlled by B-Gauge equipment. The film issubsequently stretched longitudinally in two steps and stretchedtransversely. After biaxially orientation, the film is thermally set andair corona treated on one or two sides. The following are typicalmanufacturing conditions in detail: (1) Extrusion: extrusiontemperatures 170-260° C., first chill roll temperature 10-45° C.; (2)machine direction (longitudinal) stretching: stretching roll temperatureof first step 105-120° C. and second step 115-140° C., longitudinalstretching ratio 4.5:1-6:1 for the first step and 1:1-1:2 for the secondstep; Transverse stretching: temperature of heat-up zones 150-185° C.,temperature of stretching zones 155-185° C., transverse stretching ratio7.5:1-11:1; Recycling: edges of the biaxially oriented film is recycledand fed into the line again; Heat setting: setting temperature 165-185°C.; Air corona discharge: 11 Kw.

While these descriptions directly describe the above embodiments, it isunderstood that those skilled in the art may conceive modificationsand/or variations to the specific embodiments shown and describedherein. Any such modifications or variations that fall within thepurview of this description are intended to be included therein as well.It is understood that the description herein is intended to beillustrative only and is not intended to be limitative. Rather, thescope of the invention described herein is limited only by the claimsappended hereto.

TABLE 1 Layer compositions for antifogging-antibacterial films of thepresent invention. Layer Compositions Exp A skin layer B inner layer Ccore layer D second inner layer E outer layer E1 1.0 μm — 28 μm — 1.0 μm⁽¹⁾PP-4.02% PP-97.5% E(2.5%)-P-B(4.5%) ⁽²)E(2.5)-P-B(4.5%) GMS-0.20%Terpolymer 99.75% Terpolymer-92.25% DEA-0.20% Zeolite-0.25% E-PR.Copo-2.0% E-P R.Copo-2.0% ⁽³GMS-0.20% Special Additive-0.10%⁽⁴DEA-0.20% ⁽⁵)Special Add.-0.10% Zeolite-0.23% Ag+-1.0% E2 1.0 μm — 28μm — 1.0 μm PP-4.02% PP-100.00% E(2.5%)-P-B(4.5%) E(2.5)-P-B(4.5%)Terpolymer 99.75% Terpolymer-92.25% Zeolite-0.25% E-P R.Copo-2.0%GMS-0.20% DEA-0.20% Special Additive-0.10% Zeolite-0.23% Ag+-1.0% E3 1.5μm 27 μm 1.5 μm PP-4.02% PP-97.5% E(2.5%)-P-B(4.5%) E(2.5)-P-B(4.5%)GMS-0.20% Terpolymer 99.75% Terpolymer-92.25% DEA-0.20% Zeolite-0.25%E-P R.Copo-2.0% E-P R.Copo-2.0% GMS-0.20% Special Additive-0.10%DEA-0.20% Special Additive-0.10% Zeolite-0.23% Ag+-1.0% E4 1.5 μm 27 μm1.5 μm PP-4.02% PP-97.5% E(2.5%)-P-B(4.5%) E(2.5)-P-B(4.5%) GMS-0.20%Terpolymer 97.25% Terpolymer-92.25% DEA-0.20% E-P R.Copo-2.0% GMS-0.20%E-P R.Copo-2.0% DEA-0.20% DEA-0.20% Special Additive-0.10% GMS-0.20% E-PR.Copo-2.0% Special Additive-0.10% Special Additive-0.10% Zeolite-0.25%Zeolite-0.23% Ag+-1.0% E5 1.5 μm 27 μm 1.5 μm PP-4.02% PP-97.5% PP-4.02%E(2.5)-P-B(4.5%) GMS-0.20% E(2.5)-P-B(4.5%) Terpolymer-92.25% DEA-0.20%Terpolymer-92.25 GMS-0.20% E-P R.Copo-2.0% % GMS-0.20% DEA-0.20% SpecialAdditive-0.10% DEA-0.20% E-P R.Copo-2.0% E-P R.Copo-2.0% SpecialAdditive-0.10% Special Additive-0.10% Zeolite-0.23% Zeolite-0.23%Ag+-1.0% Ag+-1.0% E6 0.75 μm 0.75 μm 27.00 μm 0.75 μm 0.75 μm ⁾PP-4.02%PP-4.02% PP-97.5% PP-4.02% PP-4.02% E(2.5)-P-B(4.5%) E(2.5)-P-B(4.5%)GMS-0.20% E(2.5)-P-B(4.5%) E(2.5)-P-B(4.5%) Terpolymer-92.25%Terpolymer-92.25% DEA-0.20% Terpolymer-92.25% Terpolymer-92.25%⁾GMS-0.20% GMS-0.20% Special Additive-0.10% GMS-0.20% GMS-0.20%⁾DEA-0.20% DEA-0.20% E-P R.Copo-2.0% DEA-0.20% DEA-0.20% SpecialAdd.-0.10% Special Additive-0.10% Special Additive- SpecialAdditive-0.10% E-P R.Copo-2.0% E-P R.Copo-2.0% 0.10% E-P R.Copo-2.0%Zeolite-0.23% Zeolite-0.23% E-P R.Copo-2.0% Zeolite-0.23% Ag+-1.0%Ag+-1.0% Zeolite-0.23% Ag+-1.0% Ag+-1.0% E7 0.75 μm 0.75 μm 27.00 μm1.50 μm PP-4.02% PP-4.02% PP-97.5% PP-4.02% E(2.5)-P-B(4.5%)E(2.5)-P-B(4.5%) GMS-0.20% E(2.5)-P-B(4.5%) Terpolymer-92.25%Terpolymer-92.25% DEA-0.20% Terpolymer-92.25% GMS-0.20% GMS-0.20%Special Additive-0.10% GMS-0.20% DEA-0.20% DEA-0.20% E-P R.Copo-2.0%DEA-0.20% Special Additive-0.10% Special Additive-0.10% SpecialAdditive- E-P R.Copo-2.0% E-P R.Copo-2.0% 0.10% Zeolite-0.23%Zeolite-0.23% E-P R.Copo-2.0% Ag+-1.0% Ag+-1.0% Zeolite-0.23% Ag+-1.0%E8 0.75 μm 0.75 μm 32.00 μm 0.75 μm 0.75 μm PP-4.02% PP-4.02% PP-97.5%PP-4.02% PP-4.02% E(2.5)-P-B(4.5%) E(2.5)-P-B(4.5%) GMS-0.20%E(2.5)-P-B(4.5%) E(2.5)-P-B(4.5%) Terpolymer-92.25% Terpolymer-92.25%DEA-0.20% Terpolymer- Terpolymer-92.25% GMS-0.20% GMS-0.20% SpecialAdditive-0.10% 92.25% GMS-0.20% DEA-0.20% DEA-0.20% E-P R.Copo-2.0%GMS-0.20% DEA-0.20% Special Additive- Special Additive-0.10% DEA-0.20%Special Additive-0.10% 0.10% E-P R.Copo-2.0% Special Additive- E-PR.Copo-2.0% E-P R.Copo-2.0% Zeolite-0.23% 0.10% Zeolite-0.23%Zeolite-0.23% Ag+-1.0% E.P R.Copo-2.0% Ag+-1.0% Ag+-1.0% Zeolite-0.23%Ag+-1.0% E9 0.75 μm 0.75 μm 32.00 μm 0.75 μm 0.75 μm PP-4.02% PP-5.02%PP-97.5% PP-5.02% PP-4.02% E(2.5)-P-B(4.5%) E(2.5)-P-B(4.5%) GMS-0.20%E(2.5)-P-B(4.5%) E(2.5)-P-B(4.5%) Terpolymer-92.25% Terpolymer-92.25%DEA-0.20% Terpolymer- Terpolymer-92.25% GMS-0.20% GMS-0.20% E-PR.Copo-2.0% 92.25% GMS-0.20% DEA-0.20% DEA-0.20% Special Additive-0.10%GMS-0.20% DEA-0.20% Special Additive- Special Additive-0.10% DEA-0.20%Special Additive-0.10% 0.10% Zeolite-0.23% Special Additive- E-PR.Copo-2.0% E-P R.Copo-2.0% E-P R.Copo-2.0% 0.10% Zeolite-0.23%Zeolite-0.23% Zeolite-0.23% Ag+-1.0% Ag+-1.0% E-P R.Copo-2.0%⁽¹⁾Polypropylene homopolymer having MFI 1.8-3.5 gr/10 min, at 230° C.,under 2.16 Kg. Load, mp = 164-166° C. ⁽²⁾E-P-B Terpolymer having MFI5.0-8.5 gr/10 min, at 230° C., under 2.16 Kg. Load, mp = 130-145° C.⁽³⁾GMS: Glycerolmonostearate ⁽⁴⁾DEA: Diethanolamine ⁽⁵⁾Special Additive:Mixture of higher fatty acid acid esters of polyvinyl alcohol orpolyether polyol.

TABLE 2 Physical-mechanical properties of the present invention (E1-E9),patented (A), and commercial (B) antifogging films. Patented FilmsProperties E1 E2 E3 E4 E5 E6 E7 E8 E9 A* B* Total thickness (μm) 30 3030 30 30 30 30 35 25 19 31 Thickness of core layer 28 28 27 27 27 27 2732 22 — — (μm) Yield (m²/kg) 36.6 36.6 36.6 36.6 36.6 36.6 36.6 31.443.9 — — Specific density (g/cm³) 0.91 0.91 0.91 0.91 0.91 0.91 0.910.91 0.91 0.91 0.92 Haze (%) 1.7 1.6 1.7 1.6 1.8 1.9 1.9 1.7 1.5 3.1 9.9Sheen (gloss), 95.2 96.6 96.8 95.2 96.2 95.8 95.3 96.3 97.4 86.6 66.445° (%) Shrinkage, 120° C./5 min (%) In MD 3.0 3.5 3.5 3.0 3.0 3.5. 3.03.0 3.2 3.5 4.5 In TD 1.0 0.5 1.0 1.0 0.5 1.0 0.5 1.0 1.0 0.25 2.0Tensile strength at break 13.8 12.6 14.2 12.9 12.3 14.1 12.8 12.3 12.113.5 13.6 (kg/mm²), in MD In TD 26.4 24.2 27.3 24.1 27.4 26.8 28.7 25.425.7 30.7 25.1 Elongation break (%) In MD 195 193 196 195 198 197 195185 193 218 183 In TD 58 57 58 59 56 58 58 55 50 50 65.9 Water vaportransmission 4.1 4.3 4.1 4.2 4.4 4.2 4.2 4.0 5.7 ≧15 — (g/m² 24 h atm20° C.) Oxygen permeability 1570 1595 1540 1615 1565 1605 1570 1450 1950≧3000 — (cc/m² 24 h atm 20° C.) Friction coefficient, 0.23 0.28 0.250.23 0.25 0.27 0.25 0.25 0.22 0.23 0.22 Film/Film Film/Metal 0.20 0.220.18 0.20 0.22 0.20 0.22 0.20 0.25 0.22 0.25 Heat seal initiation 120120 120 120 120 120 120 120 120 125 125 temperature at g/10 mm (° C.)Antifogging property** E E E E E E E E E D C Surface tension(after 40/40/ 40/ 40/ 40/ 40/ 40/ 40/ 40/ 37/39 37/32 storage for 6 months) 40 4040 40 40 40 40 40 40 (nM/m) *A - U.S. Pat. No. 4,876,146 *B - Commercialfilm **E (Excellent), D (Good), and C (Poor) in accordance with ICI“Cold-Fog” test method.

TABLE 3 Antifogging properties of the present invention (E1-E9),patented and commercial antifogging films. Antifogging properties offilms obtained by ICI “Cold-Fog” test method* Antifogging side(s)Example of the examples of No. the present invention DescriptionPerformance Rating Comments E1 A A transparent Excellent E Completelyfilm displaying Transparent no visible water E2 A As in E1 Excellent EAs in E1 E3 A As in E1 Excellent E As in E1 E4 A, E As in E1 Excellent EAs in E1 E5 A, E As in E1 Excellent E As in E1 E6 A, E As in E1Excellent E As in E1 E7 A, E As in E1 Excellent E As in E1 E8 A, E As inE1 Excellent E As in E1 E9 A, E As in E1 Excellent E As in E1 Patented —Randomly Good D Discontinuous scattered film of water transparent dropsCommercial — A complete Poor C Poor Visibility, layer of large lenseffect, transparent dripping drops As described in ICI publication 90-6Eentitled “Antifog Evaluations Tests for Agricultural and Food-PackagingFilm”:

Agricultural and Food-Packaging Film”:

Description Performance Rating Comments An opaque layer of small fogVery poor A Zero visibility droplets An opaque or transparent Poor BZero visibility layer of small fog droplets A complete layer of Poor CPoor visibility large transparent droplets Randomly scattered Good DDiscontinous large droplets film of water A transparent film withExcellent E Completely no visible water transparent

1. An antifogging coextruded and oriented film having at least threelayers comprising: an outer layer consisting of a polymer selected fromthe group consisting of polypropylene homopolymer,ethylene-propylene-n-butene terpolymers, ethylene-propylene copolymers,ethylene-n-butene copolymers, and mixtures thereof; a skin layercomprising at least one antifogging agent and a polymer selected fromthe group consisting of polypropylene homopolymer,ethylene-propylene-n-butene terpolymers, ethylene-propylene copolymers,ethylene-n-butene copolymers and mixtures thereof and a core layerbetween the outer layer and the skin layer, comprising at least oneantifogging agent and a polymer selected from the group consisting ofpolypropylene homopolymer, ethylene-propylene-n-butene terpolymers,ethylene-propylene copolymers, ethylene-n-butene copolymers and mixturesthereof.
 2. The antifogging coextruded and oriented film according toclaim 1, further comprising an inner layer between the skin layer andthe core layer characterized in that the inner layer is selected fromthe group consisting of ethylene-propylene-n-butene terpolymers,ethylene-propylene copolymers, and mixtures thereof.
 3. The antifoggingcoextruded and oriented film according to claim 2, further comprising asecond inner layer between the outer layer and the core layer,characterized in that the second inner layer is selected from the groupconsisting of ethylene-propylene-n-butene terpolymers,ethylene-propylene copolymers, and mixtures thereof.
 4. The antifoggingcoextruded and oriented film according to claim 3, characterized in thatany one of or any combination of the inner layer and the second innerlayer further comprises at least one antifogging agent.
 5. Theantifogging coextruded and oriented film according to claim 4,characterized in that any one of or any combination of at least oneantifogging agent of the skin layer, inner layer,the core layer and thesecond inner layer comprises a mixture of glycerol monostearate anddiethanolamine.
 6. The antifogging coextruded and oriented filmaccording to claim 3, characterized in that any one of or anycombination of the skin layer, inner layer, the core layer and thesecond inner layer further comprises fatty acid esters.
 7. Theantifogging coextruded and oriented film according to claim 3,characterized in that any one of or any combination of at least oneantifogging agent of the skin layer, inner layer, the core layer, andthe second inner layer further comprises a special additive selectedfrom the groups consisting of high fatty acid esters of polyvinylalcohol or polyether polyol.
 8. The antifogging coextruded and orientedfilm according to claim 3, characterized in that the skin layer, theouter layer, the inner layer and/or the second inner layer thickness isequal to or greater than 0.5 microns.
 9. The antifogging coextruded andoriented film according to claim 1, characterized in that any one of orboth the skin layer and the outer layer comprises a corona treatedsurface.
 10. The antifogging coextruded and oriented film according toclaim 1, characterized in that any one of or both the outer layer andthe skin layer is printable.
 11. The antifogging coextruded and orientedfilm according to claim 1, characterized in that any one of or both theouter layer and the skin layer is heat sealable.
 12. The antifoggingcoextruded and oriented film according to claim 1, characterized in thatthe skin layer and the outer layer are both heat sealable and also theskin layer is useful for food packaging and the outer layer is usefulfor printing.
 13. The antifogging coextruded and oriented film accordingto claim 1, characterized in that the antifogging coextruded andoriented film is biaxially stretched.
 14. The antifogging coextruded andoriented film according to claim 1, characterized in that the core layerthickness is equal to or greater than 10 microns.
 15. An antifoggingcoextruded and oriented film having at least three layers comprising: anouter layer consisting of a special additive selected from the groupconsisting of high fatty acid esters of polyvinyl alcohol or polyetherpolyol and a polymer selected from the group consisting of polypropylenehomopolymer, ethylene-propylene-n-butene terpolymers, ethylene-propylenecopolymers, ethylene-n-butene copolymers, and mixtures thereof; a skinlayer comprising at least one antifogging agent and a polymer selectedfrom the group consisting of polypropylene homopolymer,ethylene-propylene-n-butene terpolymers, ethylene-propylene copolymers,ethylene-n-butene copolymers and mixtures thereof and a core layerbetween the outer layer and the skin layer, comprising at least oneantifogging agent and a polymer selected from the group consisting ofpolypropylene homopolymer, ethylene-propylene-n-butene terpolymers,ethylene-propylene copolymers, ethylene-n-butene copolymers and mixturesthereof.